[v2.9] Cannot add a node to a specific category

Hi Everyone

I have downloaded dradis-v2.9 on windows. And I have followed every single step presented in the below link with word 2007:

I was able to do all the steps except one step which is adding a node to “word export ready” category. Whenever I click on “assign to” the node is DELETED immediately. Why I cannot assign a node to a specific category?

Second question is If I did not assign a node to “word export ready” does that mean it will not be generated in word export report?

Appreciate your help